Filtering is based on the following adjustable conditions:
- Number of monitoring agent locations reporting an error
- Duration of a period during which an Error is reported
- Number of failed tasks
- State of an Owner Device
- Specific type of error, or error code
Each new response is verified through a Filter in the following sequence:
- Error Code Check – compares a received error code (ex. HTTP “404 NOT FOUND”) with a list of Ignored Errors that are specified in a Filter.
- Task Number Check – verifies if the number of failed tasks is above, or equals, the number of tasks that are specified in a Filter.
- Monitoring Agent Locations Number Check – verifies if the number of failed monitoring locations (aka “Agents”) is above, or equals, the number of monitoring locations specified in a Filter. When the number of monitoring agent locations that report an error reaches a number specified in the Filter, the Error Duration Timer starts.
- Error Duration Timer Check – compares the duration of the reported error with a duration specified in a Filter.
- Owner Device State Check – verifies if an Owner Device is DOWN. In the case when an Owner Device is down, alert messages will not be sent (only affects filters for notifications).
When a new monitoring device is set up a <Default Filter> is automatically assigned to it. In order for the <Default Filter> to send an Alert for an Error, the Error must be detected by two, or more, monitoring Agent locations.
The <Default Filter> is recommended, in most cases, as it is designed to suppress most “nuisance” Error Alerts (such as inconsequential network “hiccups”, etc.).
However, if only one monitoring location is used with a <Default Filter>, then the Default Filter requirement, of two monitoring locations needed to confirm an error, will be ignored. In this situation, an error will be confirmed if the one monitoring location detects an error even if <Default Filter> is enabled. In fact, if the number of monitoring locations used is ever less than the required locations set-up within a filter to detect an error for a device, then the filter will be ignored.
See also: Configuring a filter